The present invention relates to electric tools powered by battery packs.
Recently, various electric tools powered by a DC power source (or battery packs), not having an AC power source, have been used in tools (e.g., building operations of houses and including cutting tools, such as circular saws, drills for boring and electric screwdrivers. For example, electric screwdrivers have included a battery pack housed in a battery housing portion, which is formed in a handle protruding laterally from a side surface of a tool body. In general, the battery pack is repeatedly used by being detached and recharged.
The battery pack generally includes a plurality of cylindrical battery cells received within a battery case. Positive and negative electric contacts and claws for engaging with the tool body are provided at an outer surface of the battery case. Known battery packs generally include two or three battery cells.
DE 10 2005 036 449 A1 discloses a technique relating to a locking mechanism for fixing a battery pack within a battery housing portion formed in a handle, where the battery pack includes three battery cells arranged in a substantially T-shape manner in a cross section.
However, in a case of the battery pack including three battery cells arranged in a substantially T-shape manner not in line, since its cross sectional shape is more similar to a circle than that of a battery pack with two battery cells, an operator is likely to select a wrong orientation for housing the battery pack when inserting the battery pack into a battery housing portion. In this context, the orientation for housing the battery pack (also, referred to as a housing orientation) means an orientation about an axis along an inserting direction of the battery (i.e., a depthwise direction of the battery housing portion). Accordingly, in the case of the battery pack with two cells, the possibility of correct orientation is one half, whereas in the case of the battery pack with three cells, it is one third, so that the operator is more likely to select its wrong orientation.
If the battery pack has been partly inserted into the battery housing portion in a wrong orientation, the battery pack should be pulled out from the battery housing portion, turned to the correct orientation and inserted into the battery housing portion again, resulting in diminished user efficiency.
Therefore, there has been a need for battery-powered tools that are improved in operability for mounting a battery pack into a battery housing portion and having a T-shape cross section.